Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a wound treatment device with a bandage and heater that are essentially planar, yet flexible, and are connected or joined by an attachment device that promotes heat transfer from the heater to the bandage and permits removal of the heater from the bandage while the bandage remains on the patient.
2. Description of the Related Art
Wounds, in general, are breaks in the integrity of the skin of a patient. A first type of wound may result from mechanical trauma that produces a cut, tear, or an abrasion. There are many instruments of causality for such wounds, including knives, glass, gravel, or a scalpel. A second type of wound may be caused by a combination of heat and pressure wherein the heat alone is insufficient to cause an outright burn. Such wounds include pressure sores, decubitus ulcers, or bed sores, and reflect an injury that is chronic in nature. A wound may also be vascular in origin. In this third type of wound, blood flow through a region may be altered sufficiently to cause secondary weakening of tissues which are eventually disrupted, thus forming a wound. In the case of arterial causes, the primary difficulty is getting oxygenated blood to the affected area. For venous causes, the primary difficulty is fluid congestion in the affected area which backs up, decreasing the flow of oxygenated blood. Because these wounds manifest underlying chronic disease processes, such as atherosclerotic vascular disease, congestive heart failure, and diabetes, these vascular injuries also are chronic in nature, forming wounds with ulcerated bases.
Heat therapy has been used to treat wounds since the days of Hippocrates, with varying results. Up to now, heat therapy for wounds has involved the application of heat under conditions that make the tissues of a wound hyperthermic. Hyperthermia impedes wound healing and may actually damage the wound tissues.
The xe2x80x9cnormalxe2x80x9d range of temperature for the human body is in the range of 37xc2x0 C.xc2x11xc2x0 C. (36xc2x0 C.-38xc2x0 C.). This is termed the xe2x80x9cnormothermicxe2x80x9d range. Humans exhibit a thermoregulatory response to core temperature changes as little as xc2x10.1xc2x0 C., wherein xe2x80x9ccorexe2x80x9d as used herein refers to interior portions of the body. This extremely tight temperature control is necessary because virtually all cellular functions, chemical reactions and enzymatic reactions are optimum at normothermia.
Surface tissue varies in temperature according to whereon the body it is located. The skin of the torso is usually hypothermic, while the skin of the legs is always hypothermic. The normal skin temperature of the distal leg is approximately 32xc2x0 C., which is considered to be xe2x80x9cmoderately hypothermicxe2x80x9d. The skin temperature of the distal leg of a patient with vascular insufficiency may be as low as 25xc2x0 C., which is xe2x80x9cseverely hypothermicxe2x80x9d. The hypothermic condition of wounds and ulcers inhibits healing. Severely hypothermic skin or wound tissue is in a state that may be termed xe2x80x9csuspended animationxe2x80x9d. In suspended animation, tissue is living, but cellular functions necessary for cell division and collagen deposition are slowed or even stopped. Further, the immune system is inhibited, allowing wounds to become heavily colonized with bacteria. The local application of heat to hypothermic skin will cause some degree of vasodilatation, resulting in an increase in local blood flow. Increased blood flow increases the subcutaneous oxygen tension (PsqO2) which, in turn, increases both collagen deposition and immune function.
Many references report that the immune system is inhibited by hypothermia and activated by mild hyperthermia (fever). Persp Biol Med:439-474. Spring 1980, reports that local body temperature is a critical factor determining host susceptibility, the location of lesions and contracting infectious diseases. New Eng J Med 305:808-814, 1981, reports that animals exposed to cold environments are more susceptible to infectious diseases, whereas exposure to high ambient temperatures often produces a beneficial result. Wound Rep Reg 2:48-56, 1994 and Acta Anaesth Scand 38:201-205, 1994, report that infections caused by a standard inoculum of e. coli or s. aureus were significantly more severe in hypothermic guinea pigs than in normothermic control animals. New Eng J Med 334:1209-1215, 1996, reports that hypothermic colorectal surgical patients had three times more wound infections (19% vs. 6%) than those who were kept normothermic during surgery with a Bair Hugger(copyright) patient warming system described in commonly assigned U.S. Pat. Nos. 5,324,320, 5,300,102 and 5,350,417. Further, six weeks of warming therapy with the Bair Hugger(copyright) patient warming system has successfully healed chronic progressive ulcers which heretofore have been resistant to standard therapies.
Currently available medical devices that apply heat to wounds include infrared lights, warm water pads, warm water bottles, whirlpools and Sitz baths. All types of lesions, such as surgical, chronic, traumatic, donor sites, infected wounds and burns, have been treated with these warming modalities. Particularly difficult has been the application of heat to open wounds such as ulcers. Treatment of a wound with infrared light requires that the wound be positioned under the light during therapy, necessitating patient immobility. Further, the infrared heat causes the wound to dry, thereby slowing the healing process. Warm water pads and bottles and electrical heating pads are cumbersome, reduce patient mobility, and are usually applied to the extremities and held in place with inconvenient wraps such as straps, hook-and-eye material or tabs. Whirlpools and Sitz baths reduce mobility and limit the duration of warming therapy due to skin maceration by the water. None of these modalities is capable of prolonged heat treatment of a wound.
There is a need for a wound treatment apparatus to conveniently treat a wound with heat therapy for a prolonged period of time, while allowing patient mobility. It is also important that the wound treatment apparatus be flexible and have a low profile for convenience of the patient. Such a wound treatment apparatus should be thermally conductive for efficient heat transfer, be convenient to operate without adversely impacting the patient, and be capable of maintaining a moist wound environment.
Preferably, the operation of the wound treatment apparatus is referred to a xe2x80x9cwound treatment areaxe2x80x9d (or xe2x80x9ctreatment areaxe2x80x9d) that may include the wound, unwounded skin adjacent the wound (the periwound), or both.
In order to deliver heat therapy to a wound treatment area it would be beneficial to employ standard bandages that are available for wound treatment. In this case, a heater may conveniently be placed on top of such a bandage and the heater/bandage apparatus may be placed on the wound treatment area. The heater and bandage are joined by an adhesive attachment device.
The bandage should preferably just cover the treatment area. Attachment of the bandage to a person""s body then becomes an important variable if the heater must be removed while the bandage remains in place. That is, removal of the heater should not disturb the attachment of the bandage to the person""s body. This requires consideration of attachment devices that act between the heater and the bandage and between the bandage and the person""s body.
The bandage is preferably thermally conductive. Thermally conductive bandages may be made of such materials as hydrogels, hydrocolloids, moist gauze, moist foam, hydrated alginates and polymeric films. In a preferred embodiment, an upper surface of the bandage includes a layer of moisture-impermeable material. With this arrangement, the bandage protects and maintains the humidity of the wound bed and the adjacent tissue.
The heater may be fashioned to primarily heat the wound, to primarily heat the periwound area, or to heat both the wound and the periwound area. Exemplary heat sources are electrical resistance heaters, chemical heaters, water pad heaters and phase-change salt heaters. In one embodiment of the invention, electrical resistance elements are embedded in or laminated to a flexible film, such as silicon, flexible rubber or flexible cloth. With this arrangement the heater is planar and flexible with a low profile. Alternatively, a water pad heater can be used. Such a heater may be made by thermo-forming two sheets of polymeric film into fluid channels and sealing the periphery. Warm water is then circulated through the pad by an external heater and pump. In other embodiments, a chemical heater or a phase-change salt heater may be used.
The attachment device may be made of a layer of polymeric film with a layer of adhesive applied to both sides which is commonly referred as xe2x80x9ctwo-faced tapexe2x80x9d or xe2x80x9cdouble-sided tapexe2x80x9d. In another embodiment, a layer of adhesive is applied to a surface of the bandage and/or the heater. The attachment device may be continuous across the entire treatment area so that uniform bonding will promote uniform conductive heat transfer from the heater to the bandage. The attachment device employs an adhesive in contrast to straps, hook-and-eye material or tabs. These latter devices allow air spaces to develop between the heater and the bandage resulting in poor and unpredictable heat transfer to the wound.
In a preferred embodiment, the heater is detachable from the bandage when it is not in use. In one embodiment, this may be accomplished by making the adhesive between the heater and the bandage less tacky than the adhesive between the bandage and the skin. Alternatively, the adhesive applied to the double-sided tape, or to either or both of the surfaces of the heater and the bandage, can be arranged in an intermittent pattern so that its pull strength is less than the pull strength of the adhesive holding the bandage to the skin surface. In embodiments where the adhesive is applied to the surface of each of the heater and the bandage, the adhesive may be selected from a group of adhesives that are not tacky to the touch but will adhere to each other.
An object of the present invention is to provide an apparatus for treating wounds with heat which has a low profile for convenience of a patient, is flexible for mobility of the patient and transfers heat by conduction to a wound and/or periwound site so as to promote heat treatment thereof.
Another object is to provide a substantially planar wound treatment apparatus that conforms to the wound and the adjacent skin.
A further object is to provide a low profile and flexible wound treatment apparatus that provides heat transfer to a wound and is easy to operate without impacting the patient""s comfort.
Still another object is to provide a low profile, flexible wound treatment apparatus that includes a heater attached to a bandage wherein the heater can be easily detached from the bandage without detaching the bandage from the skin of a patient.
Still a further object is to provide a highly mobile and convenient wound treatment apparatus which promotes heat transfer to a wound and which maintains a moist environment thereon.
Other objects and advantages of the invention will become apparent upon reading the following description taken together with the accompanying drawings.